新規太陽電池材料BaSi₂の近接蒸着による成膜技術開発

抄録

BaSi₂ has ideal optical properties for solar cell applications and can potentially realize solar cells with higher efficiency and lower cost than the mainstream crystalline Si solar cells. The close-spaced evaporation technique allows epitaxial growth of BaSi₂ films on Si substrates with scalability to large areas. The technique itself and the properties of the BaSi₂ films are reviewed in this article. Using a BaAl₄–Ni source ground in a mortar and pestle, BaSi₂ films with (001) preferred orientation are grown on Si(100) at 1000℃. Such a high temperature growth leads to film cracking. Mechanical activation of BaAl₄–Ni by ball milling lowers the BaSi₂ film formation temperature down to 700℃, resulting in crack-free films. The preferred orientation changes from (001) to (100). The crack-free BaSi₂ films have low electron concentration around 10¹⁶ cm^－3 and show clear photoconduction, suggesting potential availability for solar cells.